Kids who are overweight or obese often struggle with school work, and now new research provides clues on how excess weight may harm the developing brain.
“The main takeaway is to raise awareness about brain health consequences of obesity besides physical health consequences, especially since obesity rates are very high and continue to rise,” said study author Simone Kaltenhauser, a post-graduate research fellow in radiology and biomedical imaging at the Yale School of Medicine in New Haven, Conn.
About one in every five American kids is now obese, according to the U.S. Centers for Disease Control and Prevention.
For the study, researchers looked at several types of brain scans in more than 5,100 kids aged 9 to 10 who took part in the ongoing Adolescent Brain Cognitive Development (ABCD) study. Of these, 21% were overweight and 17.6% were obese.
What did they find? There were structural and functional brain impairments in kids who were overweight or obese when compared to kids who weren't, and these changes could contribute to poor academic performance.
Specifically, kids who were overweight or obese showed a thinning of the outermost layer of their brain (the cortex), and this has been linked with impaired executive functioning skills, such as planning and juggling multiple tasks. What's more, the integrity of the brain's white matter was impaired in the corpus callosum (which connects the brain's two hemispheres) and in the pathways within the brain's hemispheres that connect the lobes of the brain in kids who are overweight or obese.
In addition, brain networks involved in reward-based decision-making and control of behaviors showed reduced connectivity in kids who are overweight or obese.
These patterns persisted over two years, the study showed.
“Our findings provide an important potential explanation of other studies that show higher body mass index [BMI] in children is associated with poor cognitive functioning and academic achievement,” Kaltenhauser said. (BMI is a measure of body fat that takes height and weight into account.)
It's too early to say whether weight loss and increased physical activity can offset some of these brain changes, but it is possible, she noted.
“Brain plasticity, or the ability to reorganize neural pathways of children, is very high, and there is evidence in the literature that cognitive performance may increase after weight-loss interventions,” Kaltenhauser said. “The ongoing ABCD study will collect data from its participants for several more years, which will allow us to further track these changes over time.”
The findings were presented Monday at the annual meeting of the Radiological Society of North America (RSNA), in Chicago. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
Dr. Vincent Mathews said the new study helps to connect some dots between excess weight and brain changes in kids. “Prior research has shown that obesity is associated with poorer academic performance, impaired cognitive function, and lower brain volume in children,” said Mathews, chairman of radiology at the Medical College of Wisconsin in Milwaukee.
“This study shows changes in brain function and the integrity of white matter tracts related to childhood obesity, which potentially explain the impaired cognitive function and its effect on academic performance,” Mathews added.
Some questions remain, he said. "It isn't clear whether obesity precedes brain function impairment or if the latter precedes the development of obesity at this time," Mathews stressed.
Dr. Scott Kahan, director of the National Center for Weight and Wellness in Washington, D.C., said that most of the data on how obesity affects brain health is in adults. “This study adds to the literature base in kids," he noted.
More research is needed to see if carrying excess weight directly impacts the brain, or if an unhealthy diet and/or lack of physical inactivity are the culprits, or whether factors that predispose people to obesity, such as lower socioeconomic status, also contribute to poor brain development, Kahan said.
The U.S. Centers for Disease Control and Prevention offers tips on how to combat childhood obesity.
SOURCES: Simone Kaltenhauser, post-graduate research fellow, radiology and biomedical imaging, Yale School of Medicine, New Haven, Conn.; Vincent Mathews, MD, professor, chairman, department, radiology, Medical College of Wisconsin, Milwaukee; Scott Kahan, MD, director, National Center for Weight and Wellness, Washington, D.C.; Nov. 28, 2022, presentation, Radiological Society of North America (RSNA) annual meeting, Chicago